Improvement in portable derricks



UNITED STATES PATENT OFFICE.

HUGH DONNELLY, OF NEVARK, NEr JERSEY, ASSIGNOR T() PATRICK BRADY, OFSAME PLACE.

IMPROVEMENT IN PORTABLE DERRICKS,

Specification forming part of Letters Patent No. 152,349, dated June 23,U74 application tiled April 14, 1874.

To all whom it may concern:

Be it known that I, HUGH DONNELLY, of Newark, in the county of Essex andState' of New Jersey, have invented an Improvement in' PortableDerricks, of which the following is a specification:

My invention relates to an improved mode of anchoring or balancing aportable derrick. Its object is to dispense with the heavy deadweightsor guys now commonly used to prevent the dcrrick from tilting toward theweight that is bein g raised.

As these guys must be released, and the dead\veiglits removed, to permita change in the position ot' the. derrick, the objection to their use,and the value of an invention that will dispense with it, must beapparent.

A derrick embodying my invention, as represented in the drawing heretoannexed, consists of a platform, a central pulley, I1, the rear pulleyd, the forward pulley c, the hoistingrope j', the jilo-pulley G, theweight a, and the usual frame of a derrick, consisting ot the jib, theupright, the boom, &c.

The construction of my invention is as follows: rlhc hoisting-rope frunsfrom the bucket or other weight a, over a pulley, Gr, on the outer endof the boom; thence under pulley c; thence over the central pulley b,-thence under the rear pulley d; and thence off to the hoisting` power.

By this combination of pulleys, it will be found that the tendency ofthe derrick to tilt toward the weight a will be countcracted without theaid of dead-weights, guys, or other equivalents. The relative positionsof the three pulleys depend onthe height of the derrick and the bulk tobe raised, and cannot be specified further than by stating that thepulley b must always be located between the two end pulleys c and d whenthe latter are used, and that increasing the distance between theupright and the central pulley b will increase the power to overcome thetendency of thc derriek to tilt toward the weight.

rlhe hoisting-rope should generally pass under the two end pulleys, andover the central one. Manifestly, however, many variations may bc madefrom the specific mode of construction herein represented, such, forinstance, as locating the pulley b in the upright at a sudicient heightto dispense with the rear pulley d, or locating` the pulley c within theupright, or dispensing` with the pulley c under the presentconstruction. All such modifications I claim generally as within thcprinciple of my invention, which consists in using the pressure causedby the strain upon the hoisting-rope as a means of balancingthe derriek.

' I specially claimi 1. In a portable derriok or similarhoistingmachine, the wheel b, placed between the pulleys c and d,substantially as described, and for the purposes set forth.

2. In combination'with the frame and platform of a portable derrick, thewheel b, pulleys c, d, and g, and rope f, substantially as dcscribed,and for the purposes set forth.

, HUGH DONNELLY.

Witnesses:

FEED. HEWITT', HORACE HARRIS.

